1. Field of the Invention
The present invention relates to a fiber optic rod (FOR) and a process for production thereof, said fiber optic rod having high strength and toughness and good moisture resistance owing to the combination of a specific impregnating resin and fibrous reinforcement.
2. Description of the Related Art
An optical fiber cable is provided with a reinforcement which is formed by pultrusion of a composite of fibrous material and thermosetting resin or by covering with a composite of ultraviolet transmitting material and ultraviolet curable resin, followed by ultraviolet curing.
An improvement on the former is disclosed in Japanese Patent Laid-open No. 90229/1987. According to the disclosure, the process consists of impregnating a reinforcing material with a thermosetting resin, covering the impregnated reinforcing material with a thermoplastic resin, heat-curing the thermosetting resin, and removing the covering of the thermoplastic resin. The process permits a much higher production rate than the conventional pultrusion method. On the other hand, it needs additional steps for covering with a thermoplastic resin and removing it after curing. These additional steps need complicated production facilities and hinder high-speed production.
Japanese Patent Laid-open No. 225563/1988 discloses the use of an ultraviolet curable resin as a covering material of optical fiber cables. However, no one has reported using a composite of ultraviolet curable resin and fiber as a reinforcement of optical fiber cables.
Among typical ultraviolet curable resins are epoxy resins and (meth)acyrlic resins. The former are poor in productivity due to slow ultraviolet curing. The latter are poor in adhesion to the reinforcing fiber and have a large cure shrinkage. Both are inferior in performance to the composite reinforcement of heat-curable type.